Need Lens Advice

I own the 16-50 and the 50-135 and have had no problems. My good experience, though, doesn't constitute anything more than a single data point in determining the overall failure rate. The fact I've had a good experience is no more significant than the individual experiences of people reporting problems.

The trouble is, the unhappy people are louder in this discussion.

There is no evidence (beyond web accounts from unhappy individuals) that SDM lenses have any higher or lower failure rate than any other digital equipment. To say otherwise simply puts you in grassy knoll territory.

The internet petitions and lists are well-intentioned but meaningless, as they are self selected samples. Certainly they indicate there might be a problem. There are also accounts on the web that indicate the failure rate of Pentax lenses is no different from other manufacturers. That indicates there might not be a problem.

I prefer to make decisions based on verifiable evidence, and there is none here to be had, one way or the other. Meanwhile, the lenses are excellent, and I haven't been worried about them.

What is sad is the number of people out there -- like one posting above -- who believe the lens might be worth owning but are afraid to buy it because of the internet echo chamber effects.

Hope that you are, after reading more posts about opinions and experiences with SDM, not feeling so sad now,

Actually, he didn't say he himself personally was sad. He said that
IT
was sad (as in pathetic, something to be pitied) that "the number of people out there -- like one posting above -- who believe the lens might be worth owning but are afraid to buy it because of the internet echo chamber effects."

All of which was valid.

As was his other points:

His good experience doesn't constitute anything more than a single data point in determining the overall failure rate. It's no more significant than the individual experiences of people reporting problems.

Internet petitions and lists are well-intentioned but meaningless, as they are self selected samples. Certainly they indicate there might be a problem. There are also accounts on the web that indicate the failure rate of Pentax lenses is no different from other manufacturers. That indicates there might not be a problem.

knowing that there might be a valid reason that some of us are afraid to buy this lens and also that it was not the result of internet echo chamber effects but numerous reports, including some from highly credible sources.

OK, I have to call you on that. Please cite the "highly credible sources."

Good that you are lucky with your lens. SDM lenses are known for their failure

Again, I have to call you on that. Please cite the "highly credible sources."

Please note, I myself am not saying SDM failure is "high" or "low" or "somewhere in-between." I own no SDM lenses, because I tend to buy cheaper, older, used lenses. I do own one Sigma HSM lens, and it so far seems fine.

and among the SDM lenses, this one is the worst, based on variours "anecdoctal" evidence.